Because of their size and low power requirements, semiconductor light-emitting diodes occupy a large role as components in visual display systems, and there is increasing demand for components for new and improved visual display systems which will exhibit greater capabilities without having to add additional components or elements to the visual display systems.
In some display systems, a number of ways of fabricating arrays containing components that emit light of the same wavelength are known. One such article appears in the October 1967 issue of IEEE Transactions on Electron Devices, Vol. ED-14, No. 10, wherein there is described the fabrication of integrated arrays of electroluminescant diodes.
U.S. Pat. No. 3,611,069 discloses a method for making arrays of gallium arsenide phosphide diodes for use in alphanumeric light displays.
As the level of expertise in the fabrication and deployment of visual displays rose, demand for multiple color displays as an extension of this technological area surfaced with increasing intensity. It then became apparent that an obvious method for obtaining different colors could be achieved by adding additional diodes to the array; however, a drawback in the use of additional diodes resided in the disadvantage of having to add to the number of component or element positions in the array, and thereby, create further complexity and difficulty in the fabrication process.
U.S. Pat. No. 3,611,069 pertains to providing devices of multiple-layered semiconductive regions of differing conductivity forming light-emitting PN junctions at the interface of two different conductivity-type regions. In this multiple-junction structure, each diode junction ;can be independently addressed to achieve independent color control. Thus, properly doped gallium aluminum phosphide can be made to luminesce either green or rod, and by the superposition of red and green emitting junctions, yellow emission may be created.
However, the technology known to date is not known to make available, spatially uniform visual displays of more than one color using a two-terminal multi-wavelength LED device with tunnel junction, wherein two or more colors are emitted from the same device.